Theresa May has said the UK will be a “global leader” for free trade following the Brexit vote, ahead of Sunday’s G20 summit.

The message for the G20 is that Britain is open for business, as a bold, confident, outward-looking country we will be playing a key role on the world stage.

This is a golden era for UK-China relations and one of the things I will be doing at the G20 is obviously talking to president Xi about how we can develop the strategic partnership that we have between the UK and China.

12.58pm BST

The main story of today has been that the US has joined China to formally ratify the Paris agreement to curb climate-warming emissions.

Barack Obama and Xi Jinping submitted their plan to join the agreement to UN Secretary-General Ban Ki-moon, who is in China to witness the announcement, ahead of the G20 summit tomorrow.

Oxfam’s head of food and climate change campaign, Robin Willoughby, has welcomed the news that the world’s two biggest emitters, China and the US, will be ratifying the Paris agreement and bringing this historic deal closer to entry into force.

Willoughby added, however, that “whilst dozens of countries have taken the lead to make the agreement legally binding, the UK is not among them.”

12.46pm BST

Patricia Espinosa, the UN’s top climate official, has thanked the US and China for ratifying the Paris agreement.

Espinosa said in a statement Saturday that the accord offers an “opportunity for a sustainable future for every nation and every person.”

12.26pm BST

Following the earlier climate announcement, Barack Obama has reportedly told his host Xi Jinping the pair now need to have “candid talks” on topics such as human rights and maritime issues.

Reuters is reporting Obama made the comments when the pair met in Hangzhou ahead of tomorrow’s G20. Xi and Obama are due to dine together tonight after a series of bilateral meetings.

12.22pm BST

US Secretary of State John Kerry has said the US and China “demonstrated their continued, shared commitment to climate leadership” by formally joining the Paris agreement.

It turns out the American visitor being berated on the tarmac at the airport was not a reporter but Obama’s national security adviser, Susan Rice, who was stopped as she tried to reach the president’s motorcade. It was unclear if the official knew that Rice was a senior official and not a reporter.

The same official shouted at a White House press aide who was instructing foreign reporters on where to stand as they recorded Obama disembarking from the plane. “This is our country. This is our airport,” he said in English.

11.56am BST

While news surrounds Obama and Xi, German chancellor Angela Merkel has said she hopes to discuss Ukraine, Syria and refugee issues in bilateral talks on the sidelines of the G20 summit.

11.47am BST

Here are some responses to the US and China formally joining the Paris deal.

The world finally has a global climate agreement with both the US and China as formal Parties. This signals a new era in global efforts to address climate change. Both countries now need to scale and speed up their efforts in charting a future that avoids the worst impacts of climate change.

By ratifying the Paris climate agreement today, the US and China are demonstrating that the world’s two largest economies will help lead the fight against climate change – but it’s imperative that more nations join them. Cities are united in this effort, but to succeed, nations must be too – and I urge local leaders to continue pushing their national governments to ratify the Paris agreement in the months ahead.

Today’s announcement, coupled with other key countries signalling intentions to take similar action, all but assures the Paris agreement will take effect this year. Logistically, negotiations on the agreement’s detailed rules will likely take another year or two to finalise, and all countries will need to raise the ambition of their commitments under the agreement if we’re to avoid the worst impacts of climate change and reach a goal of net zero global warming emissions by mid-century. But this is an important step forward that reinforces the US and China’s continued leadership in building a robust, durable international climate framework.

This announcement provides vital momentum for the pace and scale of action required to address the climate challenge. We now urge all the other G20 members to follow this lead by the world’s two largest economies, and to take the steps required to double investment in clean energy by 2020, phase out fossil fuel subsidies swiftly, embrace carbon pricing, strengthen climate-related financial disclosure and take forward the G20 Green Finance agenda.

11.43am BST

Xi Jinping has called on other nations gathering at the G20 summit to follow China’s lead and ratify the Paris agreement. He said other G20 members should “take a leading role” and enter the agreement before the end of the year.

11.32am BST

Security at this year’s G20 is so tight that press officers of some national delegations say they are having a hard time figuring out how to brief reporters about the proceedings, the Wall Street Journal reports.

11.29am BST

Obama said he believed that history would judge today’s announcement as a “pivotal” moment in the fight against climate change.

The collaboration between the world’s top two economies, showed that it was possible for the US and China to work together, despite disagreements.

11.25am BST

Together the US and China account for 38.76% of the world’s emissions, and the countries’ joint action brings the Paris agreement substantially closer to the 55% emissions threshold needed for the agreement to enter into force. At least 55 countries must also formally join the agreement for it to take effect.

Everything you need to know about the Paris agreement is on the Climate Nexus website. The key points are as follows:

The Paris Agreement was adopted by all Parties to the UNFCCC in December 2015, but there are several formal steps to go through before the agreement enters into force in international law.

The first step: is for countries to sign the agreement. Signing signals that country’s support for the Paris agreement and its intention to align its domestic policies with the agreement terms and start the process of formally joining the agreement.

11.17am BST

Obama said cooperation was “the single best chance that we have” to save the planet as he and Xi Jinping formally entered their two nations into the Paris agreement.

“This is not a fight that any one country no matter how powerful can take alone,” Obama said of the pact. “Some day we may see this as the moment that we finally decided to save our planet.”

While it’s all smiles among the world leaders touching down in Hangzhou for the G20 summit, China is currently experiencing what western diplomats and human rights activists describe as the worst crackdown on free speech and civil society in decades.

A report this afternoon by German press agency DPA claims leading civil society organisations have been banned from taking part in the G20 summit by Chinese authorities. “Basically, there is no representation by civil society at this G20 summit,” one senior employee of a major humanitarian group is quoted as saying by DPA.

10.21am BST

Former security minister Dame Pauline Neville-Jones has said reassurances are needed from China on security issues surrounding Hinkley. Speaking on the Today programme, she said:

I think it’s unfortunate the Chinese are left empty handed, but I think it’s fair enough for [May] to want to assure herself that the security side of a very big deal like this does make sense.

The issue is the terms. Clearly Hinkley does have security implications. I think those who assert the Chinese could get into a position of trying to close this down – if that were a serious possibility, relations between the two countries would be so strained that, actually we would have taken the place over anyway. So I don’t think that’s the issue.

My impression is that we do have the notion now that there are strategic investments that we ought to be careful about, but I don’t know that we have a definition of what they are, or indeed, what ground rules should then apply.

10.15am BST

China and the United States will be hoping to publicly play down frictions over thorny issues such as the South China Sea and cyber espionage during Barack Obama’s final trip to the country as president.

But US-China tensions flared almost as soon as Obama touched down in China – under the wing of Air Force One.

Government official was not happy that reporters were under the wing of AF1. WH press aide would not back down. pic.twitter.com/C3JRVIe37K

10.05am BST

Xi Jinping has just finished delivering a keynote speech to the B20 business summit which is being held in Hangzhou, ahead of the start of the G20 tomorrow.

Xi didn’t reference his country’s decision to formally ratify the Paris climate change agreement earlier today but he did speak about China’s commitment to tackling air and water pollution and to addressing the dangers of global warming.

We will promote green development to achieve better economic performance. I have said many times that green mountains and clear water are as good as mountains of gold and silver. To protect the environment is to protect productivity and to improve the environment is to boost productivity.

We will unwaveringly pursue sustainable development and stay committed to green, low-carbon and circular development and to China’s fundamental policy of conserving resources and protecting the environment. In promoting green development we also aim to address climate change and overcapacity.

9.43am BST

World leaders are arriving in the eastern Chinese city of Hangzhou today ahead of the start of the G20 summit on Sunday. Stay with us as we live blog all of the developments that come out of the various meetings and press conferences that take place.

We have set out the government’s approach to Hinkley, we are currently considering all the component parts of that.

We have said we will make a decision this month, that remains the plan. I don’t expect one in the next few days and I don’t expect our Chinese or French partners are expecting one in the next few days.